On the error analyses of polarization measurements of the white-light coronagraph aboard ASO-S

The Advanced Space-based Solar Observatory(ASO-S) mission aims to explore the two most spectacular eruptions on the Sun: solar flares and coronal mass ejections(CMEs), and their magnetism.For the study of CMEs, the payload Lyman-alpha Solar Telescope(LST) has been proposed. It includes a traditional white-light coronagraph and a Lyman-alpha coronagraph which opens a new window to CME observations. Polarization measurements taken by white-light coronagraphs are crucial for deriving fundamental physical parameters of CMEs. To make such measurements, there are two options for a Stokes polarimeter which have been applied by existing white-light coronagraphs for space missions. One uses a single or triple linear polarizer, the other involves both a half-wave plate and a linear polarizer. We find that the former option is subject to less uncertainty in the derived Stokes vector propagating from detector noise.The latter option involves two plates which are prone to internal reflections and may have a reduced transmission factor. Therefore, the former option is adopted as our Stokes polarimeter scheme for LST. Based on the parameters of the intended linear polarizer(s) colorPol provided by CODIXX and the half-wave plate 2-APW-L2-012 C by Altechna, it is further shown that the imperfect maximum transmittance of the polarizer significantly increases the variance amplification of Stokes vector by at least about 50% when compared with the ideal case. The relative errors of Stokes vector caused by the imperfection of colorPol polarizer and the uncertainty due to the polarizer assembly in the telescope are estimated to be about 5%. Among the considered parameters, we find that the dominant error comes from the uncertainty in the maximum transmittance of the polarizer.     

Multi-spacecraft Observations of CIR-Associated Ion Increases During the Ulysses 2007 Ecliptic Crossing

The period between 21 June and 8 October, 2007 (Carrington rotations 2058 to 2061), comprising the Ulysses ecliptic plane crossing, was characterized by low solar activity. Excluding the small solar energetic particle events observed during July, the ion increases observed in the inner heliosphere between 100?keV/n and 10?MeV/n were associated with Corotating Interaction Regions (CIRs). In this work, we investigate CIR-related ion increases using multipoint observations from Ulysses, ACE, and the twin STEREO spacecraft. The ballistic backmapping technique has been used to correlate in situ observations of these spacecraft and remote-sensing observations of coronal holes. Although the radial, longitudinal and latitudinal separation of the spacecraft (except Ulysses) are relatively small, we find discrepancies when a detailed comparison of narrow structures like stream interfaces and CIR-associated shocks is performed. Therefore we concentrate on the two CIR events from day 5 to day 10 of August 2007 and from day 25 to day 31 of August 2007, which lend themselves to a more undisturbed comparison. Using the multi-spacecraft measurements we could determine a radial gradient of 230±30% AU^?1, which is consistent with previous results by van Hollebeke et al. (J. Geophys. Res. 83, 4723, 1978) of ～?350% AU^?1 using Helios and Pioneer data.

     

湖南芙蓉锡矿床锡矿石和有关花岗岩的40Ar-39Ar年龄及其地球动力学意义

在研究和介绍湖南芙蓉锡矿矿床地质特征的基础上,对云英岩型锡矿石中的白云母和与成矿有关的骑田岭角闪黑云花岗岩中的黑云母进行了40Ar-39Ar年龄测定,获得角闪黑云花岗岩的坪年龄为(157.5±0.3)Ma;三门云英岩锡矿石的坪年龄为(156.1±0.4)Ma;淘洗窝云英岩锡矿石的坪年龄(160.1±0.9)Ma.这3组测年数据很一致,不仅精确地反应出成岩成矿的时间限制,而且表明了花岗岩成岩与锡矿成矿的密切关系.此外,三组数据坪年龄一致显示出,在成岩成矿之后矿体未受到后期热事件的扰动.芙蓉锡矿床是湘南大型钨锡多金属矿集区的组成部分,也是华南地区中生代钨锡成矿两大高峰期之一的160～135 Ma期间形成的代表性矿床,可能为中国东部地球动力学体制调整时晚期岩石圈减薄过程中的产物.     

Meltwater and the global ocean conveyor: northern versus southern connections

The sensitivity of the ocean circulation to changes in North Atlantic surface fluxes has become a major factor in explaining climate variability. The role of the Antarctic Bottom Water in modulating this variability has received much less attention, limiting the development of a complete understanding of decadal to millennial time-scale climate change. New analyses indicate that the southern deepwater source may change dramatically (e.g., experience a decrease of as much as two thirds during last 800 years). Such change can substantially alter the ocean circulation patterns of the last millennium. Additional analyses indicate that the Southern Hemisphere led the Northern Hemisphere changes in some of the glacial cycles of Pleistocene, implying a seesaw-type oscillation of the global ocean conveyor. The potential for melting of sea ice and ice sheets in the Antarctica associated with global warming can cause a further slowdown of the southern deepwater source. These results demand an assessment of the role of the Southern Ocean in driving changes of the global ocean circulation and climate. Systematic model simulation targeting the ocean circulation response to changes in surface salinity in the high latitudes of both Northern and Southern Hemispheres demonstrate that meltwater impacts in one hemisphere may lead to a strengthening of the thermohaline conveyor driven by the source in the opposite hemisphere. This, in turn, leads to significant changes in poleward heat transport. Further, meltwater events can lead to deep-sea warming and thermal expansion of abyssal water, that in turn cause a substantial sea-level change even without a major ice sheet melting.     

The behaviour of outer radiation belt electrons (> 1·5 MeV) during a geomagnetically disturbed time on 8 March 1970 and its relationship to magnetospheric processes

Omnidirectional intensities of electrons with energies E_e > 1·5 MeV detected by a low orbiting polar satellite (GRS-A/AZUR) in the outer radiation belt are examined during disturbed times including the main phase of a very strong geomagnetic storm on 8 March 1970. The particle intensity features are discussed in relationship with proposed magnetospheric processes. It is found that a superposition of the two following effects can explain the particle behavior in the trapping region:(A) Radial diffusion. After the southward turning of the interplanetary field an inward motion of both the energetic electron belt and the plasmapause took place. This effect was observed at L > 3 R_E and we attribute it to enhanced magnetospheric electric field fluctuations. Later, a strong interplanetary shock impinged upon the magnetosphere which was related to the triggering of intense magnetospheric substorms; a further inward diffusion occurred at L ? 3 R_E, accompanied by an inward movement of the electron slot. A rough estimation of the diffusion coefficient leads to a power spectrum of the electric field fluctuations which seems to be consistent with experimentally determined power spectra (Mozer, 1971).(B) Adiabatic response to ring current changes. Large energetic electron intensity decreases within the outer radiation belt are shown to be adiabatic changes due to ring current variations. The influence of the inflation of the magnetosphere due to the developing ring current is simultaneously observed by the decrease of the solar proton outoff (1·7-2·5 MeV).